1

我正在使用 JavaMail API 来解析电子邮件标头。在以 KB 为单位的电子邮件文件大小的正常情况下,它不会在 JVM 中占用太多内存。但是,在带有附件的大型电子邮件文件(35MB+)的情况下,它会在 JVM 中使用巨大的空间。

是否有任何可能的方法来修改电子邮件标题而不在内存中加载电子邮件内容?

我正在做这样的事情:

Properties props = System.getProperties();
Session mailSession = Session.getDefaultInstance(props, null);
InputStream source = new FileInputStream(emlFile);
MimeMessage message = new MimeMessage(mailSession, source);

message.addHeader("X-Header","HeaderValue1");
message.addHeader("Y-Header", "HeaderValue2");
message.saveChanges();
Enumeration headerschange = message.getAllHeaders();

StringBuilder headerString = new StringBuilder();
while (headerschange.hasMoreElements()) {
      Header h = (Header) headerschange.nextElement();
      headerString = headerString.append(h.getName() + ": " + h.getValue() + "\n");
}
System.out.println("headerString::::::::::::::::::::"+headerString.toString());
4

1 回答 1

0

作为 EML 文件的邮件存储为文本文件。典型的 eml 如下所示:

X-Mozilla-Status: 0001
X-Mozilla-Status2: 00000000
Received: from tomts25-srv.bellnexxia.net
        (tomts25.bellnexxia.net [209.226.175.188])
    by tactika.com (8.9.3/8.9.3) with ESMTP id NAA07621
    for <real@rgagnon.com>; Sun, 1 Feb 2004 13:25:33 -0500 (EST)
Date: Sun, 01 Feb 2004 13:31:40 -0500
From: real gagnon <real@rgagnon.com>
Reply-To: real@rgagnon.com
User-Agent: Mozilla/5.0
   (Windows; U; Windows NT 5.1; en-US; rv:1.4)
   Gecko/20030624 Netscape/7.1 (ax)
X-Accept-Language: en-us, en
MIME-Version: 1.0
To: real@rgagnon.com
Subject: Example for HowTo
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 7bit
X-UIDL: oP#!!c]^!!1;-!!T@1"!


This is an example

因此,您可以读取文件,直到找到两个新行。

try {
            BufferedReader reader = new BufferedReader(new FileReader(new File("C:\\test\\test.eml"))); 

            StringBuilder headerString = new StringBuilder();
            String line;
            int newLines = 0;
            while((line = reader.readLine()) != null) {
                if(line.equals("\n")) {
                    newLines++;
                    if (newLines == 2) {
                        //Body starts here
                        break;
                    }
                } else {
                    headerString.append(line).append("\n");
                }
            }
            System.out.println("headerString::::::::::::::::::::"+headerString.toString());
            reader.close();
        } catch(IOException e) {
            e.printStackTrace();
        }

您可以在此处找到确切的规格

http://www.ietf.org/rfc/rfc0822.txt

于 2017-05-31T11:25:17.310 回答